Microemulsions are thermodynamically-stable, optically-clear emulsions having submicron-sized droplets suspended in a continuous phase. These emulsions form spontaneously and typically consist of an aqueous phase, an organic phase, and a surfactant/co-surfactant component.
Previous data suggest that ethanol is required to maintain stable oil-in-water microemulsions. However, topical application of ethanol has a drying effect on the skin. Additionally, ethanol and compositions containing ethanol are extremely flammable. For these reasons, ethanol-containing microemulsions for topical application have seen limited commercial use.